Spin Transport And Magnetization Reversal In The Vertically Oriented Magnetic Multilayer Films

After giant magnetoresistance(GMR)and transfer torque(STT),there has been another significant discovery in the field of spintronics in recent years.Spin current from heavy metal into the adjacent magnetic layer utilizing spin Hall effect(SHE)in the heavy metal/ferromagnetic metal structures,can induce the magnetization reversal of the magnetic layer.The device based on SHE has a simpler structure and are expected to be used in the next generation of magnetic random memory(MRAM)to further improve storage density and reduce power consumption.In this work,topics of study include the optimization of Pt,Co,Ta films using magnetron sputtering deposition system,and the preparation of Ta/Pt/Co/Pt and Ta/Pt/Co/Ta magnetic multilayer films on Si/Si O2 substrates.We focus on the multilayer film surface morphology,vertical anisotropy,the anomalous hall effect,and the anisotropic field.The main contents are as follows:(1)Through varying the deposition pressure and other experimental conditions,we optimize(111)-oriented Pt,Co,Ta films with quality surface roughness.The vertical oriented Pt/Co/Pt magnetic multilayer film were prepared.The abnormal Hall curve was measured with a good thermal stability and un-dependence on the current density.The anisotropic field under different temperature fit by the Hall resistance with in-plane magnetic field reaches 1.1 T at low temperature,and 3000 Oe at room temperature.(2)Ta seed layer was used to optimize the vertical oriented Ta/Pt/Co/Ta magnetic multilayer films with remanence ratio close to 1.The films exhibiting abnormal Hall curves with un-dependent current density,are good vertical anisotropy and good thermal stability.The anisotropic field fit by the Hall resistance with in-plane magnetic field is as high as 0.9 T at room temperature,and 1.4 Oe at 10 K.According to the data fitting,the anisotropic field at room temperature is 9362 Oe,and the effective spin hall Angle is 0.61.Through XAS test,the source of the larger anisotropic field and spin hall Angle of the system is the spin orbit coupling interaction between the Co upper and lower interfaces.However,the current density of magnetization switching is 106A/cm2.To sum up,in this paper we experimentally prepared and optimized the vertical oriented Pt/Co/Pt and Pt/Co/Ta magnetic multilayer films with good thermal stability.In the Ta/Pt/Co/Ta multilayer films a large anisotropy field and magnetization reversal at low current densities was obtained.